Discussion
In this case, no optic nerve swelling or signal changes were evident on imaging, but fundus examination revealed mild erythema of the optic nerve papilla. Although this finding could be attributed to iritis, the possibility of optic neuritis caused by an autoimmune mechanism in IgG4-related disease could not be ruled out. However, the visual field findings were not consistent with those commonly observed in optic papillitis. Moreover, brain MRI findings suggested optic chiasm compression due to pituitary enlargement. The patient’s visual acuity and visual field defects improved following pituitary gland enlargement after steroid treatment, suggesting that pituitary gland enlargement and pituitary scrofula were the main pathophysiology of vision loss and visual field defects.
The ophthalmologic clinical hallmark of IgG4-related ocular disease is bilateral lacrimal gland enlargement with three features: suborbital nerve enlargement, exophthalmos, and pressure optic neuropathy2). IgG4-related optic neuropathy is commonly caused by compression of the optic nerve by enlargement of the lacrimal glands or other intraorbital tissues2)5)6)7)8). Few studies have reported on optic neuropathy caused by compression of the optic chiasm by an enlarged pituitary gland as in the present case3)7)8). Although bilateral hemianopsia is generally observed with pituitary enlargement, the present case showed mild visual field defects in not only the auriculolateral lower one-quarter blindness but also the nasal lower one-quarter region. A previous study9) found visual field defects in only one eye in two of 10 patients with symmetrical pituitary enlargement. Because the present case also showed optic chiasm compression due to pituitary enlargement, it is possible that it caused an atypical visual field defect and associated visual acuity impairment.
Alternatively, as other studies have shown infiltration of IgG4-positive plasma cells around the trigeminal nerve in the same disease2), a deep infiltrative or inflammatory mechanism may be involved in this case of optic neuropathy.
In conclusion, it is necessary to consider that the effects of IgG4-related disease may be involved when patients complain of vision loss and visual field impairment.
Declarations :
  1. State of Ethics: Ethical approval is not required for this study in accordance with local or national guidelines. Written informed consent was obtained from the patient for publication of the details of their medical case and any accompanying images.
  2. Conflict of Interest: Not applicable.
  3. Funding Sources- No funding was obtained for this study.
  4. Author contributions and Data Availability: Shintaro Kohno, Hitoshi Tabuchi and Atsuki Fukushima evaluated the findings of patients and collected data. Shintaro Kohno and Atsuki Fukushima wrote the manuscript. All data generated or analysed during this study are included in this article.